text: // ----------------------------------------------------------------------------
  // -                        Open3D: www.open3d.org                            -
  // ----------------------------------------------------------------------------
  // The MIT License (MIT)
  //
  // Copyright (c) 2018 www.open3d.org
  //
  // Permission is hereby granted, free of charge, to any person obtaining a copy
  // of this software and associated documentation files (the "Software"), to deal
  // in the Software without restriction, including without limitation the rights
  // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  // copies of the Software, and to permit persons to whom the Software is
  // furnished to do so, subject to the following conditions:
  //
  // The above copyright notice and this permission notice shall be included in
  // all copies or substantial portions of the Software.
  //
  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  // FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  // IN THE SOFTWARE.
  // ----------------------------------------------------------------------------
  
  #include "Open3D/IO/ClassIO/TriangleMeshIO.h"
  
  #include <unordered_map>
  
  #include "Open3D/Utility/Console.h"
  #include "Open3D/Utility/FileSystem.h"
  
  namespace open3d {
  
  namespace {
  using namespace io;
  
  static const std::unordered_map<
          std::string,
          std::function<bool(const std::string &, geometry::TriangleMesh &)>>
          file_extension_to_trianglemesh_read_function{
                  {"ply", ReadTriangleMeshFromPLY},
                  {"stl", ReadTriangleMeshFromSTL},
          };
  
  static const std::unordered_map<
          std::string,
          std::function<bool(const std::string &,
                             const geometry::TriangleMesh &,
                             const bool,
                             const bool)>>
          file_extension_to_trianglemesh_write_function{
                  {"ply", WriteTriangleMeshToPLY},
                  {"stl", WriteTriangleMeshToSTL},
          };
  
  }  // unnamed namespace
  
  namespace io {
  
  std::shared_ptr<geometry::TriangleMesh> CreateMeshFromFile(
          const std::string &filename) {
      auto mesh = std::make_shared<geometry::TriangleMesh>();
      ReadTriangleMesh(filename, *mesh);
      return mesh;
  }
  
  bool ReadTriangleMesh(const std::string &filename,
                        geometry::TriangleMesh &mesh) {
      std::string filename_ext =
              utility::filesystem::GetFileExtensionInLowerCase(filename);
      if (filename_ext.empty()) {
          utility::PrintWarning(
                  "Read geometry::TriangleMesh failed: unknown file "
                  "extension.\n");
          return false;
      }
      auto map_itr =
              file_extension_to_trianglemesh_read_function.find(filename_ext);
      if (map_itr == file_extension_to_trianglemesh_read_function.end()) {
          utility::PrintWarning(
                  "Read geometry::TriangleMesh failed: unknown file "
                  "extension.\n");
          return false;
      }
      bool success = map_itr->second(filename, mesh);
      utility::PrintDebug(
              "Read geometry::TriangleMesh: %d triangles and %d vertices.\n",
              (int)mesh.triangles_.size(), (int)mesh.vertices_.size());
      if (mesh.HasVertices() && !mesh.HasTriangles()) {
          utility::PrintWarning(
                  "geometry::TriangleMesh appears to be a geometry::PointCloud "
                  "(only contains "
                  "vertices, but no triangles).\n");
      }
      return success;
  }
  
  bool WriteTriangleMesh(const std::string &filename,
                         const geometry::TriangleMesh &mesh,
                         bool write_ascii /* = false*/,
                         bool compressed /* = false*/) {
      std::string filename_ext =
              utility::filesystem::GetFileExtensionInLowerCase(filename);
      if (filename_ext.empty()) {
          utility::PrintWarning(
                  "Write geometry::TriangleMesh failed: unknown file "
                  "extension.\n");
          return false;
      }
      auto map_itr =
              file_extension_to_trianglemesh_write_function.find(filename_ext);
      if (map_itr == file_extension_to_trianglemesh_write_function.end()) {
          utility::PrintWarning(
                  "Write geometry::TriangleMesh failed: unknown file "
                  "extension.\n");
          return false;
      }
      bool success = map_itr->second(filename, mesh, write_ascii, compressed);
      utility::PrintDebug(
              "Write geometry::TriangleMesh: %d triangles and %d vertices.\n",
              (int)mesh.triangles_.size(), (int)mesh.vertices_.size());
      return success;
  }
  
  }  // namespace io
  }  // namespace open3d
  